Endocrine tumors, such as insulinoma, are rare but notoriously difficult to treat surgically due to their small size and poor contrast using white light. Endocrine tumors, such as ovarian cancer, are common but equally difficult to treat surgically, with improved survival dependent on complete cytoreduction. Similarly, normal endocrine tissues, such as the thyroid gland and adrenal gland, can often be difficult to locate during surgery due to adhesions and overlying fascia. Our hypothesis is that near-infrared (NIR) fluorophores targeted to endocrine glands and their tumors will provide surgeons with sensitive, specific, and real-time image- guidance after a single, pre-operative, intravenous injection. When used with an appropriate intraoperative imaging system, NIR fluorescent light from 700 to 900 nm can provide surgeons with real-time localization of normal and diseased tissue, without changing the look of the surgical field. As part of a previously funded Bioengineering Research Partnership (BRP) grant, we have developed the FLARE (Fluorescence-Assisted Resection and Exploration) image-guided surgery system. FLARE provides real-time imaging of surgical anatomy (i.e., color video) simultaneously with two independent channels of NIR fluorescent light (700 nm and 800 nm emission). One NIR channel is typically reserved for the tissue to be resected (e.g., tumor) while the other is reserved for tissue that needs to be avoided (e.g., nerves, blood vessels, normal glands, etc.). FLARE has already been translated to the clinic where it is being used in breast cancer sentinel lymph node (SLN) mapping, lung cancer SLN mapping, and plastic surgery. The resection of endocrine gland tumors (e.g., insulinoma and ovarian cancer) and the avoidance of normal endocrine tissue (e.g., thyroid and adrenal glands) represent a significant unmet clinical need, with no available contrast agents. In collaboration with the Henary/Strekowski/Patonay laboratory at Georgia State University, recognized leaders in the field of fluorophore chemistry, we have developed novel NIR fluorophores tailored to endocrine imaging (endocrine-specific NIR fluorophores; ESNFs). Sharing structural and chemical similarities with naturally occurring hormones and drugs, ESNFs provide high contrast for image-guided surgery after a single intravenous injection into mice, rats, and pigs. The specific aims of this grant are focused on the synthesis of three new chemical classes of ESNFs, scale-up from analytical to preparative production, and optimization of their optical and chemical properties. Completion of these aims will lay the foundation for future clinical testing of ESNFs during image-guided surgery.